In order to explore those areas which may be dangerous for human (for example, different planets, underground tunnels or caves), exploration robots are used. Exploration robots comprise various sensors for detecting objects in the area they are sent and for identifying the characteristics of the said objects. One of the sensors used in the said exploration robots is tactile sensors. By means of the tactile sensors, presence of certain objects and some physical features thereof such as pressure can be detected.
The conventional tactile sensors comprise a light source positioned under an elastic surface and a light sensing element for sensing the amount of the light reflected from the said surface, as disclosed in US2010155579A1. In such tactile sensors, when a force is applied on the elastic surface, the said surface approaches to the light source and the light sensing element. As a result of such approach, the amount of light incident on the light sensing element increases. The amount of light sensed by the light sensing element and resilience properties of the surface are used to calculate the amount of force applied to the surface. However, in this embodiment, the number of light sources that may be positioned under the unit surface and of the light sensing elements are limited, and it is cumbersome to process data received from a high number of light sensing elements.
Said problems are solved by a module disclosed in WO2014011126A1. The said module comprises an elastic material, which is covered with a layer providing light reflection; a CMOS or CCD image sensor; at least one light source; a plurality of first fiber optic cables, a tips of which are separated from surrounding environment via said layer by being located under the layer and other tips of which are in connection with said light source, wherein said first fiber optic cables carry light beams from the light source to said layer; a plurality of second fiber optic cables, a tips of which are separated from surrounding environment via said layer by being located under the layer and being directed towards the layer and other tips of which are in connection with said image sensor so that each second fiber optic cable is paired with one pixel of the image sensor, wherein light beams reflected from the layer are transferred to the image sensor by said second fiber optic cables; a processor which calculates every individual force applied to the layer according to light intensity changes of each pixel connected with a second fiber cable, of a photo frame generated by the image sensor in response to the displacement of the layer by using image processing techniques. In the module disclosed in WO2014011126A1, when the elastic material contacts to an object, a deformation is generated in the elastic material and the said layer (e.g. displacement of the layer towards the fiber optic cables). As a result of such displacement, the amount of light reflected from the layer to the fiber optic cable is changed. Said change in the amount of light is detected as a color change in the photo frame generated in the image sensor. The processor applies image processing techniques to the said photo frame so as to measure color changes of the photo, and thus the amount of displacement of the layer. Based on the amount of displacement calculated, the force applied on the elastic material is also calculated. However, due to the fact that in the said embodiment detection is only performed based on the level of light, an improvement is needed.
Another patent document U.S. Pat. No. 4,547,668A discloses a two-dimensional pressure sensor. Said pressure sensor comprises a light source; a matrix of light transmitting fiber endings comprising a plurality of fibers for transmitting said light from said light source and a plurality of fibers for receiving reflected light; a transmitting fiber sub-array comprising endings of said transmitting fibers located a distance from said matrix of light transmitting fiber endings, said endings located to receive light from said light source; a receiving fiber sub-array, comprising endings of said receiving fibers located a distance from said matrix of light transmitting fiber endings; a retro-reflective material located a distance above said matrix; a semi-transparent deformable medium located between said matrix and said retro-reflective material, said semi-transparent deformable medium supporting said retro-reflective material; a flexible membrane located adjacent said retro-reflective material side farthest from said matrix; and means located adjacent said receiving fiber sub-array, for detecting said reflected light transmitted by said light fibers from said matrix to said receiving fiber sub-array.
Another patent document WO2005029028A1 discloses an optical tactile sensor. Said optical tactile sensor comprises a sensing part comprising a transparent elastic body and a plurality of marker groups provided in said body, each marker group being comprised of a number of colored markers, with markers constituting different marker groups having different colors for each group, said elastic body having an arbitrary curved surface; a photographing device for taking an image of behavior of colored markers when said curved surface of elastic body is contacted by an object to obtain image information of markers, and a force vector distribution reconstructing device including a transfer function by which a force vector applied to the surface is reconstructed from information as to the behavior of markers that is obtained from the image information of markers, and said force vector distribution reconstructing device reconstructing forces applied to said surface from said information as to the behavior of markers by using the transfer function.